It has been proposed to treat age-related macular degeneration (AMD) by irradiating the choroidal neovascularization (CNV) underlying the retina that is associated with AMD with ionizing radiation (such as beta or x-ray radiation). See, generally, U.S. Pat. No. 6,875,165 and U.S. Pub. Appln. No. 2003/0179854, both of which are incorporated herein by reference. Certain apparatus for the intraocular delivery of radiation, either epi-retinally or sub-retinally, and methods of their use are disclosed in the co-pending U.S. application Ser. No. 11/056,763, filed Feb. 11, 2005 and Ser. No. 11/228,030, filed Sep. 15, 2005, identified above.
As noted in the above-referenced patents and applications, Beta radiation, and some forms of x-ray radiation, are advantageous for treating AMD because the dose delivered by such radiation sources decays roughly with the square of distance in materials with similar density to water (such as human tissue). Therefore, by accurately positioning the radiation source or emitter in close proximity to the target tissue (in this case the CNV, and/or taking steps to avoid irradiating non-target tissue by, e.g. the use of masks or attenuating substances and filters, a therapeutic radiation dose can be delivered to the target tissue, while delivering little or no dose to non-target tissues (such as surrounding ocular or non-ocular structures). The present application discloses a variety of methods and apparatus for accomplishing such accurate targeting of treatment.